This invention relates to methods for the production of 1-menthol which is used as a medicament or perfume and of its intermediate pulegone.
There are some reports on the hydrogenation reaction into pulegone from piperitenone which can be easily synthesized from mesityl oxide and methyl vinyl ketone. There are an example 1) reported by J. Solodar et al. in J. Org. Chem., vol. 43, p. 1787, 1978, in which the hydrogenation is carried out using a Rh complex which uses cyclohexylanisylmethylphosphine as the ligand and an example 2) reported by P. L. Maux et al. in Tetrahedron, vol. 44, p. 1409, 1988, in which the hydrogenation is carried out using a diphenylneomenthylphosphine-Co complex.
Regarding reports on pulegol from pulegone, there is an example described by T. Ohkuma et al. in Synlett, p. 467, 1997, in which a catalyst system of (S)-BINAP-Ru-(S,S)-diphenylethylenediamine-KOH is used.
Regarding the synthesis of pulegone, the method 1) can synthesize it with a selectivity of about 90% but its optical purity is a low value of 33% ee, and DMF (dimethylformamide) is used in the reaction solvent, so that this method is not industrially applicable. Also, the method 2) can synthesize it only with a selectivity of 55% and an optical purity of 15% ee, so that they are not industrially applicable levels.
In addition, the ligand to be used in the synthesis of pulegol is a combination of (S)-BINAP and (S,S)-diphenylethylenediamine, and since optically active substances are used for both of them, this method has a problem of high catalyst cost.
The invention contemplates solving the illustrative problems shown in the following items 1) to 3).
1) Since there are three positions in piperitenone where hydrogenation can be effected, it is necessary for obtaining pulegone to increase position selectivity of hydrogenation. That is, it is necessary to select a catalyst, namely a ligand and a transition metal, which can attain superior selectivity and optical yield to those of conventionally used ligands including a monodentate phosphine such as cyclohexylanisylmethylphosphine, phenylanisylmethylphosphine or cyclohexyl-o-tert-butylphenylmethylphosphine and a bidentate phosphine such as DIPAMP: 1,2-bis[(o-methoxyphenyl)phenylphosphino]ethane or DIOP: 2,3-o-isopropylidene-2,3-dihydroxy-1,4-bis-(diphenylphosphino)butane, and to examine solvent systems and additives which exert influences thereon.
2) Regarding preparation of pulegol from pulegone, significant result is obtained by a prior art ruthenium-diamine-potassium hydroxide system, so that it is expected to obtain equivalent catalytic activity and selectivity by changing it to an inexpensive catalyst.
3) The method to obtain menthol by hydrogenating pulegol can be carried out using a heterogeneous hydrogenation catalyst, but concern has been directed toward the development of a catalyst system having more higher selectivity.
The following describes the invention in detail.
The piperitenone to be used in the invention can be prepared by allowing mesityl oxide to react with methyl vinyl ketone in the presence of potassium hydroxide (cf. JP-B-57-47168; the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) or by condensing mesityl oxide with 4-diethylamino-2-butanone.
In the invention, the 2-position olefin of piperitenone is hydrogenated as the first hydrogenation reaction. The reaction formula is shown below. 
As the ligand to be used in the catalyst for hydrogenation of the 2-position olefin of piperitenone, there is an optically active phosphine represented by a general formula (2) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (2) of the present invention. R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (2) include tertiary phosphines described in JP-A-61-63690 and JP-A-62-265293 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples.
2,2xe2x80x2-Bis(diphenylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cBINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis[di(p-tolyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cTol-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis[di(3,5-xylyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cDM-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis[di(3,5-di-tert-butylphenyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9c(t-Bu)2-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis[di(4-methoxy-3,5-dimethylphenyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cDMM-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis(dicyclohexylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cCy-BINAPxe2x80x9d hereinafter), and
2,2xe2x80x2-bis(dicyclopentylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cCp-BINAPxe2x80x9d hereinafter).
As another ligand to be used in the catalyst for the first hydrogenation reaction, there is an optically active phosphine represented by a general formula (3) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (3) of the present invention. R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (3) include tertiary phosphines described in JP-A-4-139140 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples.
2,2xe2x80x2-Bis{diphenylphosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cH8-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis{di-p-tolylphosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cp-Tol-H8-BINAPxe2x80x9d hereinafter),
2,2xe2x80x2-bis{di-(3,5-xylyl)phosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cDM-H8-BINAPxe2x80x9d hereinafter), and
2,2xe2x80x2-bis{di-(4-methoxy-3,5-dimethylphenyl)phosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cDMM-H8-BINAPxe2x80x9d hereinafter).
As still another ligand to be used in the catalyst for the first hydrogenation reaction, there is an optically active phosphine represented by a general formula (4) 
wherein R represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms, R2 represents hydrogen atom or a lower alkyl group having from 1 to 4 carbon atoms, R3 represents hydrogen atom methyl group, methoxy group or a halogen atom, and R4 represents methyl group or methoxy group, or R3 and R4 may be coupled together to form methylenedioxy group.
In this general formula (4) of the present invention. R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (4) include tertiary phosphines described in JP-A-11-269,185 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples.
((5,6),(5xe2x80x2,6xe2x80x2)-Bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(diphenylphosphine) (to be referred to as xe2x80x9cSEGPHOSxe2x80x9d hereinafter),
((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di-p-tolylphosphine) (to be referred to as xe2x80x9cp-Tol-SEGPHOSxe2x80x9d hereinafter),
((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di-3,5-xylylphosphine) (to be referred to as xe2x80x9cDM-SEGPHOSxe2x80x9d hereinafter),
((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di-4-methoxy-3,5-dimethylphenylphosphine) (to be referred to as xe2x80x9cDMM-SEGPHOSxe2x80x9d hereinafter),
((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di-4-methoxy-3,5-tert-butylphenylphosphine) (to be referred to as xe2x80x9cDTBM-SEGPHOSxe2x80x9d hereinafter), and
((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(dicyclohexylphosphine) (to be referred to as xe2x80x9cCy-SEGPHOSxe2x80x9d hereinafter).
In addition to the above, the following optically active phosphines can be cited.
2,2xe2x80x2-Dimethyl-6,6xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cBIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-p-tolylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-3,5-xylylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-4-methoxy-3,5-dimethylphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-4-t-butoxy-3,5-dimethylphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDTBM-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(dicyclohexylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cCy-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cMeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di-p-tolylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-MeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di-3,5-xylylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-MeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di-4-methoxy-3,5-dimethylphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-MeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di-4-t-butoxy-3,5-dimethylphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDTBM-MeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(dicyclohexylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cCy-MeO-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-p-tolylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-CM-BIPHEMPxe2x80x9d hereinafter),
2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-3,5-xylylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-CM-BIPHEMPxe2x80x9d hereinafter), and
2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di-4-methoxy-3,5-dimethylphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-CM-BIPHEMPxe2x80x9d hereinafter).
According to the invention, the 2-position olefin of piperitenone is hydrogenated with a complex consisting of the optically active phosphine represented by the general formula (2), (3) or (4) and a transition metal, and the desirable catalyst to be used in this hydrogenation is a transition metal complex consisting of an optically active phosphine containing a transition metal selected from rhodium, iridium and ruthenium and a transition metal. Most desirably, the hydrogenation is carried out by further adding an ammonium salt, a phosphonium salt or an alkali metal salt to such a complex consisting of an optically active phosphine and a transition metal.
Since each of these tertiary phosphines exists in (+)- and (xe2x88x92)-isomer forms, one of them is selected in response to the absolute configuration of pulegone of the intended optically active compound. That is, (S)-isomer is used for obtaining (1R) isomer, and (R)-isomer is used for obtaining (1S) isomer.
Rhodium Complex
As an illustrative example of the production method of a rhodium complex, it can be synthesized by allowing bis(cycloocta-1,5-diene)rhodium(I) tetrafluoroborate to react with an optically active bidentate phosphine (L) in accordance with the method described on pages 339 to 344 of Jikken-Kagaku-Kouza 4th Edition, Vol. 18, Organic Metal Complex, 1991, edited by The Chemical Society of Japan, published by Maruzen. The following can be cited as illustrative examples of the rhodium complex.
[Rh(cod)(L)]ClO4,
[Rh(cod)(L)]PF6,
[Rh(cod)(L)]BF4,
[Rh(cod)(L)]BPh4,
[Rh(cod)(L)]OTf,
[Rh(cod)(L)]OTs,
[Rh(cod)(L)]SbF6,
[Rh(cod)(L)]OCOCF3,
[Rh(cod)(L)]OCOC2F5,
[Rh(cod)(L)]OCOC3F7,
[Rh(nbd)(L)]ClO4,
[Rh(nbd)(L)]PF6,
[Rh(nbd)(L)]BF4,
[Rh(nbd)(L)]BPh4,
[Rh(nbd)(L)]OTf,
[Rh(nbd)(L)]OTs,
[Rh(nbd)(L)]SbF6,
[Rh(nbd)(L)]OCOCF3,
[Rh(nbd)(L)]OCOC2F5,
[Rh(nbd)(L)]OCOC3F7,
Rh(cod)(L)Cl,
Rh(nbd)(L)Cl,
Rh(cod)(L)Br,
Rh(nbd)(L)Br,
Rh(cod)(L)I, and
Rh(nbd)(L)I.
Each of the abbreviations used in the above formulae indicates following respective compound.
L: Optically active phosphine represented by the general formula (2), (3) or (4),
OTf: trifluoromethanesulfonate,
OTs: p-toluenesulfonate,
Ph: phenyl,
cod: 1,5-cycooctadiene, and
nbd: norbornadiene.
Ruthenium Complex
Regarding the method for producing a ruthenium complex, it can be prepared by heating and stirring [Ru(p-cymene)X2]2 (X represents chlorine, bromine, and iodine) and L in methylene chloride and ethanol by the method described in a document (K. Mashima, K. Kusano, T. Ohta, R. Noyori and H. Takaya, J. Chem. Soc., Chem. Commn., 1208 (1989)). The following can be cited as illustrative examples of the ruthenium complex.
[RuCl(benzene)(L)]Cl,
[RuBr(benzene)(L)]Br,
[RuI(benzene)(L)]I,
[RuCl(p-cymene)(L)]Cl,
[RuBr(p-cymene)(L)]Br,
[RuI(p-cymene)(L)]I,
[RuCl(mesitylene)(L)]Cl,
[RuBr(mesitylene)(L)]Br,
[RuI(mesitylene)(L)]I,
[RuCl(hexamethylbenzene)(L)]Cl,
[RuBr(hexamethylbenzene)(L)]Br,
[RuI(hexamethylbenzene)(L)]I,
[{RuCl(L)}2(xcexc-Cl)3][NH2Me2],
[{RuCl(L)}2(xcexc-Cl)3][NH2Et2],
[{RuCl(L)}2(xcexc-Cl)3][NH2Pr2], and
[{RuCl(L)}2(xcexc-Cl)3][NH2i-Pr2].
Iridium Complex
The iridium complex can be prepared by allowing L to react with [Ir(cod)(CH3CN)2]BF4 while stirring in tetrahydrofuran in accordance with the method described in a document (K. Mashima, T. Akutagawa, X. Zhang, T. Taketomi, H. Kumobayashi and S. Akutagawa, J. Organomet. Chem., 1992, 428, 213). The following can be cited as illustrative examples of the iridium complex.
[Ir(cod)(L)]ClO4,
[Ir(cod)(L)]PF6,
[Ir(cod)(L)]BF4,
[Ir(cod)(L)]BPh4,
[Ir(cod)(L)]OTf,
[Ir(cod)(L)]OTs,
[Ir(cod)(L)]SbF6, 
[Ir(cod)(L)]OCOCF3,
[Ir(cod)(L)]OCOC2F5,
[Ir(cod)(L)]OCOC3F7,
[Ir(nbd)(L)]Cl)4,
[Ir(nbd)(L)]PF6,
[Ir(nbd)(L)]BF4,
[Ir(nbd)(L)]BPh4,
[Ir(nbd)(L)]OTf,
[Ir(nbd)(L)]OTs,
[Ir(nbd)(L)]SbF6,
[Ir(nbd)(L)]OCOCF3,
[Ir(nbd)(L)]OCOC2F5,
[Ir(nbd)(L)]OCOC3F7,
Ir(cod)(L)Cl,
Ir(nbd)(L)Cl,
Ir(cod)(L)Br,
Ir(nbd)(L)Br,
Ir(cod)(L)I, and
Ir(nbd) (L)I.
Since ethyl acetate (EtOAc) is excellent in both selectivity and optical yield as the solvent in the presence of a xe2x80x9ccomplex consisting of an optically active phosphine and a transitionmetalxe2x80x9d selected from rhodium, iridium and ruthenium, a system in which the selectivity becomes high in the EtOAc solvent was established by a simple screening test. As the result, it was found that a quaternary ammonium salt or a quaternary phosphnium salt represented by a general formula (10)
xe2x80x83R5R6R7R8ABxe2x80x83xe2x80x83(10)
(wherein each of R5 , R6, R7 and R8 means an alkyl group having from 1 to 16 carbon atoms, phenyl group or benzyl group, A means nitrogen atom or phosphorus atom, and B means a halogen atom such as chlorine, bromine or iodine, a carboxylate or a sulfonate) is useful, and its illustrative examples include quaternary ammonium salts such as Me4NCl, Me4NBr, Me4NI, Et4NCl, Et4NBr, Et4NI, Bu4NCl, Bu4NBr, Bu4NI, (Benzyl)Me3NCl, (Benzyl)Me3NBr, (Benzyl)Me3NI, (Benzyl)Et3NCl, (Benzyl)Et3NBr, (Benzyl)Et3NI, (C8H17)Me3NCl, (C8H17)Me3NBr, (C8H17)Me3NI, (C16H33)Me3NCl, (C16H33)Me3NBr, (C16H33)Me3NI, Me4NOTf, Me4NOTs, Me4NOAc, Me4NOCOCF3, n-Bu4NOTf, n-Bu4NOTs, n-Bu4NOAc and n-Bu4NOCOCF3, and quaternary phosphonium salts such as MePh3PCl, MePh3PBr, MePh3PI, EtPh3PCl, EtPh3PBr, EtPh3PI, BuPh3PCl, BuPh3PBr, BuPh3PI, Ph4PCl, Ph4PBr, Ph4PI, (C6H13)Ph3PCl, (C6H13)Ph3PBr, (C6H13)Ph3PI, (C7H15)Ph3PCl, (C7H15)Ph3PBr, (C7H15)Ph3PI, (C8H17)Ph3PCl, (C8H17)Ph3PBr, (C8H17)Ph3PI, (C16H33)Ph3PCl, (C16H33)Ph3PBr, (C16H33)Ph3PI, (C16H33)Bu3PCl, (C16H33)Bu3PBr, (C16H33)Bu3PI, ClPPh3CH2PPh3Cl, ClPPh3(CH2)2PPh3Cl, ClPPh3(CH2)3PPh3Cl, ClPPh3(CH2)4PPh3Cl, ClPPh3(CH2)5PPh3Cl, ClPPh3(CH2)6PPh3Cl, BrPPh3CH2PPh3Br, BrPPh3(CH2)2Ph3Br, BrPPh3(CH2)3Ph3Br, BrPPh3(CH2)4Ph3Br, BrPPh3(CH2)5Ph3Br, BrPPh3(CH2)6Ph3Br, IPPh3CH2PPh3I, IPPh3(CH2)2PPh3I, IPPh3(CH2)3PPh3I, IPPh3(CH2)4PPh3I, IPPh3(CH2)5PPh3I and IPPh3(CH2)6PPh3I.
Also useful is a salt represented by a general formula (11):
MZxe2x80x83xe2x80x83(11)
(wherein M means a metal of Li, Na or K, and Z means a halogen atom such as Cl, Br or I), and its illustrative examples include metal salts such as LiCl, LiBr, LiI, NaCl, NaBr, NaI, KCl, KBr and KI.
Ammonium salts such as (Bn)Et3NCl, (Bn)Et3NBr and (Bn)Et3NI and phosphonium salts such as such as BuPh3PCl, BuPh3PBr, BuPh3PI, (C6H13)Ph3Br and BrPPh3(CH2)4PPh3Br can be selected, from which high selectivity is obtained (in which Bn is benzyl group, Et is ethyl group, Ph is phenyl group, and Bu is butyl group).
Regarding the ligand, DM-BINAP can be selected from BINAPs, DM-H8-BINAP can be selected from H8-BINAPs and DTBM-SEGPHOS can be selected from SEGPHOS, from which high selectivity is obtained.
This reaction is carried out under a hydrogen pressure of about from 5 to 100 Kg/cm2 (0.5 to 10 Mpa), at a reaction temperature of about from 10 to 100xc2x0 C. and for a reaction time of about from 5 to 20 hours. Also, amount of the transition metalxe2x80x94optically active phosphine complex to be used is about from 1/5,000 to 1/50,000 mole based on piperitenone. Amount of the additive (an ammonium salt, a phosphonium salt or an alkali metal) to be used is about from 0.2 to 2.0 equivalent based on the transition metalxe2x80x94optically active phosphine complex.
Preferred among the solvents are without solvent, or in a solvent such as THF, acetone and ethyl acetate.
According to the invention, pulegol represented by the formula (6) is obtained by, as the second hydrogenation reaction, hydrogenating pulegone represented by the formula (5) with a ruthenium-phosphine-amine complex. The reaction formula is shown below. 
As the second hydrogenation reaction method, a system of a ruthenium complex-amine-base is most excellent in hydrogenating the obtained pulegone (5), and a result of examination revealed that an achiral ligand can be used as the ruthenium complex. Examples of the ruthenium complex having such a ligand are shown below. In the following examples, Et means ethyl group, dmf means dimethylformamide and n is from 1 to 5.
Ru2Cl4((S)-binap)2(NEt3),
Ru2Cl4((S)-tol-binap)2(NEt3),
Ru2Cl4((S)-dm-binap)2(NEt3),
RuCl2((S)-binap)(dmf)n,
RuCl2((S)-tol-binap)(dmf)n,
RuCl2((S)-dmbinap)(dmf)n,
RuCl2(PPh3)3,
RuCl2[(p-tolyl)3P]3,
RuCl2[(o-tolyl)3P]3,
RuCl2(bpbp),
RuCl2(1,2-diphos)2,
RuCl2(1,3-diphos)2,
RuCl2(1,4-diphos)2,
RuCl2(1,5-diphos)2,
RuCl2(1,6-diphos)2 
Further, each abbreviation in the above formulae indicates the following respective compound.
bpbp: 2,2xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-biphenyl,
1,2-diphos: 1,2-bis(diphenylphosphino)ethane,
1,3-diphos: 1,3-bis(diphenylphosphino)propane,
1,4-diphos: 1,4-bis(diphenylphosphino)butane,
1,5-diphos: 1,5-bis(diphenylphosphino)pentane,
1,6-diphos: 1,6-bis(diphenylphosphino)hexane
The amine compounds include a primary amine compound, a secondary amine compound, and a diamine compound. The following amine compounds are typical example: primary amine compounds such as methylamine, ethylamine, propylamine, butylamine, penthylamine, hexylamine, cyclopenthylamine, cyclohexylamine and benzylamine; secondary amine compounds such as dimethylamine, diethylamine, dipropylamine, dibutylamine, dipenthylamine, dihexylamine, dicyclopenthylamine, dicyclohexylamine, dibenzylamine, diphenylamine, phenylethylamine, piperidine and piperadine; and diamine compounds such as methylenediamine, 1,2-ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4-butanediamine, 2,3-butanediamine, 1,2-cyclopentanediamine, 1,2-cyclohexanediamien, N-methylethylenediamine, N,Nxe2x80x2-dimethylethylenediamine, N,N,Nxe2x80x2-trimethylethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine, o-phenylenediamine, p-phenylenediamine and 1,2-diphenylethylenediamine.
As the amine, 1,2-ethylenediamine, 1,3-propanediamine, 1,4-butanediamine and 1,2-diphenylethylenediamine are preferably selected, of which 1,2-ethylenediamine and 1,3-propanediamine are most superior.
As the base, metal salts each represented by the following formula (12)
Mxe2x80x2Yxe2x80x83xe2x80x83(12)
wherein Mxe2x80x2 represents an alkali metal or alkaline earth metal and Y represents a hydroxy, alkoxy, mercapto, naphthyl group or carbonate, or quaternary ammonium salts can be employed. Specific examples include LiOH, LiOMe, LiOEt, LiOi-Pr, LiOt-Bu, NaOH, NaOMe, NaOEt, NaOi-Pr, NaOt-Bu, KOH, KOMe, KOEt, KOi-Pr, KOt-Bu, KC10H8, Li2CO3, K2CO3 and Na2CO3. Quaternary ammonium salts are also usable.
As the base, pottassium hydroxide (KOH) and potassium t-butoxide (KOt-Bu) are preferably selected.
Amount of the catalyst is about from {fraction (1/1,000)} to {fraction (1/30,000)} mole based on the substitute pulegone. Amount of the amine is about from 1 to 2 equivalent based on the catalyst. Amount of the base is about from 0.5 to 100 equivalent, or preferably about from 10 to 50 equivalent, based on the catalyst.
In the invention, any liquid solvent is usable insofar as it can solubilize reaction raw materials (pulegone) and catalyst system. Examples include aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents such as pentane and hexane, halogen-containing hydrocarbon solvents such as methylene chloride, ether solvents such as ether and tetrahydrofuran, alcohol solvents such as methanol, ethanol, isopropanol, butanol, and benzylalcohol, and hetro-atom-containing organic solvents such as acetonitrile, DMF and DMSO. The target product is an alcohol so that alcohol solvents are most suited, with isopropanol being more preferred.
The amount of the solvent is judged from the solubility of the reaction substrate and economy. When isopropanol is employed, reaction can be effected at a low concentration of 1% or less or in a nearly solventless manner, though depending on the kind of the substrate. Preferred is 0.1 to 2.0 by volume. The hydrogen pressure within a range of 1 to 100 Kg/cm2 (0.1 to 10 MPa) is desired, with 5 to 50 Kg/cm2 (0.5 to 5 MPa) being more preferred.
Although the reaction is preferably conducted within a range of 0 to 150xc2x0 C., with 10 to 50xc2x0 C. being more preferred. The reaction time differs with the concentration of the reaction substrate or reaction condition such as temperature and pressure, but reaction is completed within several minutes to 30 hours.
It is desirable that the thus formed pulegol is subjected to the subsequent reaction after increasing its chemical purity and optical purity by recrystallization. High purity pulegol can be obtained by recrystallizing it using a hydrocarbon solvent such as hexane, cyclohexane, heptane, pentane, octane or isooctane. Amount of the hydrocarbon solvent to be used is from 0.5 to 10 times, preferably from 1 to 3 times, based on pulegol. The temperature at the time of crystallization is selected within the range of from xe2x88x9270xc2x0 C. to 0xc2x0 C., and generally carried out within the range of from xe2x88x9240xc2x0 C. to 0xc2x0 C.
According to the invention, 1-menthol represented by the formula (7) is obtained by, as the third hydrogenation reaction, hydrogenating pulegol represented by the formula (6) with a transition metal catalyst. The reaction formula is shown below. 
As the third hydrogenation, the thus obtained pulegol (6) is hydrogenated with a generally and frequently used heterogeous hydrogen catalyst. Examples include Raney nickel, platinum oxide, platinum black, palladium black, rhodium black, palladium-carbon, iridium-carbon, rhodium-carbon, ruthenium-carbon, osmium-carbon, palladium-alumina, palladium-silica and palladium-silica-alumina. Specific examples include Raney nickel, palladium-carbon, iridium-carbon, rhodium-carbon, ruthenium-carbon, palladium-alumina, palladium-silica and palladium-silica-alumina, and most specific examples includes palladium-carbon and palladium-silica-alumina.
This reaction is carried out under a hydrogen pressure of about from 5 to 50 Kg/cm2 (0.5 to 5 MPa), at a reaction temperature of about from 20 to 100xc2x0 C. and for a reaction time of about from 5 to 20 hours. Also, mount of the catalyst to be used is about from 0.01 to 1.0 wt. % based on pulegol.
Preferred among the solvents are without solvent, or in a solvent such as THF, acetone and ethyl acetate.
Also, a homogeneous catalyst in the form of a ruthenium-phosphine-dicarboxylate complex is used in the third hydrogenation of the thus obtained pulegol (6).
As the ligand to be used in the catalyst for hydrogenating the olefin of pulegol, there is an optically active phosphine represented by a general formula (2) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (2) of the present invention, R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (2) include tertiary phosphines described in JP-A-61-63690 and JP-A-62-265293 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples. 2,2xe2x80x2-Bis (diphenylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cBINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis[di(p-tolyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cTol-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis[di(3,5-xylyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cDM-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis[di(3,5-di-tert-butylphenyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9c(t-Bu)2-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis[di(4-methoxy-3,5-dimethylphenyl)phosphino]-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cDMM-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis(dicyclohexylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cCy-BINAPxe2x80x9d hereinafter), and 2,2xe2x80x2-bis(dicyclopentylphosphino)-1,1xe2x80x2-binaphthyl (to be referred to as xe2x80x9cCp-BINAPxe2x80x9d hereinafter).
Also, among optically active phosphines represented by a general formula (3) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms.
In this general formula (3) of the present invention, R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (3) include tertiary phosphines described in JP-A-4-139140 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples. 2,2xe2x80x2-Bis{diphenylphosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cH8-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis{di(p-tolyl)phosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cp-Tol-H8-BINAPxe2x80x9d hereinafter), 2,2xe2x80x2-bis{di-(3,5-xylyl)phosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cDM-H8-BINAPxe2x80x9d hereinafter), and 2,2xe2x80x2-bis{di-(4-methoxy-3,5-dimethylphenyl)phosphino}-5,5xe2x80x26,6xe2x80x2,7,7xe2x80x2,8,8xe2x80x2-octahydrobinaphthyl (to be referred to as xe2x80x9cDMM-H8-BINAPxe2x80x9d hereinafter).
Also, among optically active phosphines represented by a general formula (4) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms, R2 represents hydrogen atom or a lower alkyl group having from 1 to 4 carbon atoms, R3 represents hydrogen atom methyl group, methoxy group or a halogen atom, and R4 represents methyl group or methoxy group, or R3 and R4 may be coupled together to form methylenedioxy group.
In this general formula (4) of the present invention, R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
Examples of the optically active phosphine to be desirably used according to this general formula (4) include tertiary phosphines described in JP-A-11-269,185 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), and the following can be cited as illustrative examples.
((5,6), (5xe2x80x2,6xe2x80x2)-Bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(diphenylphosphine) (to be referred to as xe2x80x9cSEGPHOSxe2x80x9d hereinafter), ((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di(p-tolyl)phosphine) (to be referred to as xe2x80x9cp-Tol-SEGPHOSxe2x80x9d hereinafter), ((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di(3,5xylyl)phosphine) (to be referred to as xe2x80x9cDM-SEGPHOSxe2x80x9d hereinafter), ((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di(4-methoxy-3,5-dimethylphenyl)phosphine) (to be referred to as xe2x80x9cDMM-SEGPHOSxe2x80x9d hereinafter), ((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di(4-methoxy-3,5-tert-butylphenyl)phosphine) (to be referred to as xe2x80x9cDTBM-SEGPHOSxe2x80x9d hereinafter), and ((5,6),(5xe2x80x2,6xe2x80x2)-bis(methylenedioxy)biphenyl-2,2xe2x80x2-diyl)bis(di(cyclohexyl)phosphine) (to be referred to as xe2x80x9cCy-SEGPHOSxe2x80x9d hereinafter). Also included are 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cBIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(p-tolyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(3,5-xylyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(4-methoxy-3,5-dimethylphenyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(4-t-butoxy-3,5-dimethylphenyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDTBM-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(cyclohexyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cCy-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cMeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di(p-tolyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-MeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di(3,5-xylyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-MeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di(4-methoxy-3,5-dimethylphenyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-MeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di(4-t-butoxy-3,5-dimethylphenyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDTBM-MeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethoxy-6,6xe2x80x2-bis(di(cyclohexyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cCy-MeO-BIPHEPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(p-tolyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cp-Tol-CM-BIPHEMPxe2x80x9d hereinafter), 2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(3,5-xylyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDM-CM-BIPHEMPxe2x80x9d hereinafter), and 2,2xe2x80x2-dimethyl-3,3xe2x80x2-dichloro-4,4xe2x80x2-dimethyl-6,6xe2x80x2-bis(di(4-methoxy-3,5-dimethylphenyl)phosphino)-1,1xe2x80x2-biphenyl (to be referred to as xe2x80x9cDMM-CM-BIPHEMPxe2x80x9d hereinafter).
Also, as still another ligand to be used in the catalyst for the third hydrogenation reaction, there is a phosphine represented by a general formula (8)
R12Pxe2x80x94(CH2)nxe2x80x94PR12xe2x80x83xe2x80x83(8)
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms, and n is an integer of from 1 to 7.
In this general formula (8) of the present invention, R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl. The following can be exemplified as suitably useful phosphines of the general formula (8).
Bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, 1,5-bis(diphenylphosphino)pentane, 1,6-bis(diphenylphosphino)hexane, 1,7-bis(diphenylphosphino)heptane, bis(di(p-tolyl)phosphino)methane, 1,2-bis(di(p-tolyl)phosphino)ethane, 1,3-bis(di(p-tolyl)phosphino)propane, 1,4-bis(di(p-tolyl)phosphino)butane, 1,5-bis(di(p-tolyl)phosphino)pentane, 1,6-bis(di-p-tolyl)phosphino)hexane, 1,7-bis(di(p-tolyl)phosphino)heptane, bis(di(3,5-xylyl)phosphino)methane, 1,2-bis(di(3,5-xylyl)phosphino)ethane, 1,3-bis(di(3,5-xylyl)phosphino)propane, 1,4-bis(di(3,5-xylyl)phosphino)butane, 1,5-bis(di(3,5-xylyl)phosphino)pentane, 1,6-bis(di(3,5-xylyl)phosphino)hexane, 1,7-bis(di(3,5-xylyl)phosphino)heptane, bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)methane, 1,2-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino) ethane, 1,3-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)propane, 1,4-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)butane, 1,5-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)pentane, 1,6-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)hexane, 1,7-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)heptane, bis(di(3,5-difluorophenyl)phosphino)methane, 1,2-bis(di(3,5-difluorophenyl)phosphino)ethane, 1,3-bis(di(3,5-difluorophenyl)phosphino)propane, 1,4-bis(di(3,5-difluorophenyl)phosphino)butane, 1,5-bis(di(3,5-difluorophenyl)phosphino)pentane, 1,6-bis(di(3,5-difluorophenyl)phosphino)hexane, 1,7-bis(di(3,5-difluorophenyl)phosphino)heptane, bis(di(3,5-ditrifluoromethylphenyl)phosphino)methane, 1,2-bis(di(3,5-ditrifluoromethylphenyl)phosphino)ethane, 1,3-bis(di(3,5-ditrifluoromethylphenyl)phosphino)propane, 1,4-bis(di(3,5-ditrifluoromethylphenyl)phosphino)butane, 1,5-bis(di(3,5-ditrifluoromethylphenyl)phosphino)pentane, 1,6-bis(di(3,5-ditrifluoromethylphenyl)phosphino)hexane and 1,7-bis(di(3,5-ditrifluoromethylphenyl)phosphino)heptane.
In addition to the above, there is a phosphine represented by a general formula (9) 
wherein R1 represents an aryl group which may have a substituent group or a cycloalkyl group having from 3 to 8 carbon atoms, each of R7 to R10 represents hydrogen atom, methyl group, methoxy group, phenyl group, a halogen atm or trifluoromethyl group, or R7 and R8, R8 and R9 or R9 and R10 together form methylenedioxy group or R8 and R9 together from a cycloalkyl ring.
In this general formula (9) of the present invention, R1 is a phenyl group which may have a substitutent group, a naphthyl group which may have substitutent group or a cycloalkyl group having from 3 to 8 carbon atoms.
Examples of the substituents thereof include lower alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl, and isobutyl; halogen atoms such as fluorine, chlorine, and bromine; lower alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy, and butoxy; halogenated lower alkyl groups such as trifluoromethyl and trichloromethyl, and benzyloxy.
Preferred examples of R1 include phenyl, 4-tolyl, 3-tolyl, 4-methoxyphenyl, 3,5-xylyl, 3,5-di-tert-butylphenyl, 4-methoxy-3,5-dimethylphenyl, 4-methoxy-3,5-di-tert-butylphenyl, naphthyl, cyclohexyl and cyclopentyl.
The following can be exemplified as suitably useful phosphines of the general formula (9). 1,2-Bis(diphenylphosphino)benzene, 1,2-bis(di(p-tolyl)phosphino)benzene, 1,2-bis(di(3,5-xylyl)phosphino)benzene, 1,2-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)benzene, 1,2-bis(di(3,5-difluoropheyl)phosphino)benzene, 1,2-bis(di(3,5-di-trifluoromethylphenyl)phosphino)benzene, 1,2-bis(diphenylphosphino)-4,5-methylenedioxybenzene, 1,2-bis(di(p-tolyl)phosphino)-4,5-methylenedioxybenzene, 1,2-bis(di(3,5-xylyl)phosphino)-4,5-methylenedioxybenzene, 1,2-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)-4,5-methylenedioxybenzene, 1,2-bis(di(3,5-difluorophenyl)phosphino)-4,5-methylenedioxybenzene, 1,2-bis(di(3,5-ditrifluoromethylphenyl)phosphino)-4,5-methylenedioxybenzene, 2,3-bis(diphenylphosphino)naphthalene, 2,3-bis(di(p-tolyl)phosphino)naphthalene, 2,3-bis(di(3,5-xylyl)phosphino)naphthalene, 2,3-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)naphthalene, 2,3-bis(di(3,5-difluorophenyl)phosphino)naphthalene, 2,3-bis(di(3,5-ditrifluorophenyl)phosphino)naphthalene, 2,3-bis(diphenylphosphino)-5,6,7,8-octahydronaphthalene, 2,3-bis(di(p-tolyl)phosphino)-5,6,7,8-octahydronaphthalene, 2,3-bis(di(3,5-xylyl)phosphino)-5,6,7,8-octahydronaphthalene, 2,3-bis(di(4-methoxy-3,5-di-tert-butylphenyl)phosphino)-5,6,7,8-octahydronaphthalene, 2,3-bis(di(3,5-difluorophenyl)phosphino)-5,6,7,8-octahydronaphthalene and 2,3-bis(di(3,5-di-trifluoromethylphenyl)phosphino)-5,6,7,8-octahydronaphthalene.
Ruthenium Dicarboxylate Complex
As an illustrative example of the method for the production of ruthenium complexes, they can be synthesized in accordance with the method described by Ohta et al. in Inorg. Chem., vol. 27, p. 566, 1998. The following can be cited as illustrative examples of the dicarboxylate complex.
Ru(OAc)2(L)
Ru (OCOPh)2 (L)
Ru(OCOC2H5)2(L)
Ru(OCOC3H7)2(L)
Ri(OCO-i-C3H7)2(L)
Ru(OCOC4H9)2(L)
Ru(OCO-t-C4H9)2(L)
Ru(OCOCH2OCO)(L)
Ru(OCOC2H4OCO)(L)
Ru(OCOC3H6OCO)(L)
Ru(OCOC4H8OCO)(L)
Abbreviations in the above formulae indicate the following compounds.
L: an optically active phosphine represented by the general formula (2), (3), (4), (8) or (9)
Ac: acetyl
Ph: phenyl
As the third hydrogenation, the most high selectivity was obtained when the pulegol (6) was hydrogenated using a ruthenium dicarboxylate complex. Though other reaction conditions are not different from those of general hydrogenation, the reaction is carried out at a reaction temperature of from 20 to 100xc2x0 C. for a reaction period of from 5 to 20 hours under an hydrogen pressure of from 5 to 50 kg/cm2 (0.5 to 5 MPa), without solvent or in a solvent such as toluene, ethyl acetate, methanol, ethanol, 2-propanol, methylene chloride or tetrahydrofuran. 
By the method found by the invention in which piperitenone is hydrogenated by an optically active phosphine ligand and a transition metal complex, it become possible to produce pulegone with high position selectivity and also with high optical yield. In addition, 1-menthol can be produced by carrying out selective hydrogenation of pulegone with a ruthenium-phosphine-amine complex in the presence of base to obtain pukegol and then hydrogenation it with a transition metal catalyst. That is, there provided a method for producing 1-menthol by an inexpensive method with high yield, by repeating hydrogenation reaction there times.
The invention is illustratively described in the following with reference to inventive and comparative examples, though the invention is not restricted by these examples.
In this connection, the following instruments were used for the measurement of physical properties of the compounds obtained in the inventive and comparative examples.
NMR DRX500 (mfd. by Bruker)
1H-NMR (500 MHz; internal standard: tetramethylsilane)
31P-NMR (202 MHz; internal standard: 85% phosphoric acid)
GLC 5890-II (mfd. by Hewlett Packard)
GC-Column Conversion ratio: FFAP 30 mxc3x970.53 mm (GL Science Ltd.)
Optical yield: Chiraldex B-TA 30 mxc3x970.25 mm (ASTEC)